The present invention relates in general to parts assembly systems and, more particularly, to systems including apparatus and methods of assembling component parts of dental floss dispensers.
Tooth decay and dental disease can be caused by bacterial action resulting from the formation of plaque about the teeth and/or the entrapment of food particles between the teeth and interstices therebetween. The removal of plaque and entrapped food particles reduces the incidence of caries, gingivitis, and mouth odors as well as generally improving oral hygiene. Conventional brushing has been found to be inadequate for removing all entrapped food particles and plaque. To supplement brushing, dental flosses and tapes have been recommended. The term xe2x80x9cdental flossxe2x80x9d, as used herein, is defined to include both dental flosses, dental tapes, threads and any similar article.
Dental floss is typically distributed in a compact dispenser from which a user may conveniently extract desired lengths of floss for dental cleansing purposes. The dispenser normally includes a dispenser case having a releasable lid. Typically enclosed within the dispenser case are an insert, a spool of dental floss rotatably supported by the insert, and a cutter bar carried by the insert. The free or xe2x80x9ctailxe2x80x9d end of the spool of floss is usually threaded through an eyelet provided in the insert near the top of the dispenser as well as the cutting blade portion of the cutter bar. In order to draw a length of floss from the dispenser, a user grasps the tail end of the floss and pulls until a desired length has been drawn, and then cuts the drawn length using the cutter bar. As the user pulls the floss from the dispenser, the spool rotates, thereby allowing the floss to be unwound from the spool.
In the manufacture of the various components of a conventional dental floss dispenser, experience has shown that, for purposes of economy and performance, the aforesaid insert should preferably be formed from molded plastic material whereas the cutter bar functions best when fabricated from stamped metal sheet. Metal is the material preferred for the cutter bar as it produces a cutting blade portion having a cutting edge sufficiently sharp to permit easy cutting of the dental floss. Being formed from such disparate materials, however, the cutting blade must be physically joined to the insert during a dispenser manufacturing process to produce a combined cutter bar and insert subassembly.
At present, at least two types of automated machinery have been developed to unite a dental floss dispenser cutter bar with its associated insert. According to a first design, two conveyors are employed to deliver separate streams of inserts and cutter bars to an assembly device. The insert conveyor serially transports the inserts side-by-side in a substantially horizontal orientation. As the leading insert reaches the assembly device it is urged laterally into an elongated channel. Once in the channel, it is pushed therealong by a push rod. At the completion of the push rod stroke, the insert is intended to abut a stop member at one end of the channel such that cutter bar receiving structure provided on the insert is exposed to receive a cutter bar. The leading cutter bar in a stream of serially arranged cutter bars delivered by the cutter bar conveyor is then press-fit onto the insert""s cutter bar receiving structure by extension of a suitable linear operator means such as a pneumatic piston and cylinder assembly, or the like. Upon retraction of the linear operator means the united cutter bar and insert subassembly is supposed to fall from a discharge opening in the bottom of the channel and into a collection bin from which it may be recovered for assembly (along with a spool of dental floss) into a dispenser case.
It has been discovered, however, that gravity acting alone or with the slight assistance provided by the retraction of the linear operator means is frequently insufficient to positively dislodge the cutter bar/insert subassembly from the channel whereby it may fall through the channel discharge opening. Consequently, the entire cutter bar and insert assembly line must be brought to a halt and the jammed subassembly physically removed by the machine operator. Furthermore, the relatively long stroke of the push rod oftentimes causes the insert to become misaligned in its path of travel along the channel. In many instances such misalignment is serious enough to prevent a cutter bar from being placed onto the insert receiving structure. In addition, the machine may jam and damage may result to the cutter bar, the insert or both. In such case, production must again be stopped to free the jam. As will be appreciated, work stoppages of the types described result in considerable downtime, labor costs and waste part expenses.
An alternative approach has been to feed inserts substantially vertically into radially directed holding slots of a rotatable, horizontally disposed, multiple station assembly wheel. Cutter bars are press-fit laterally onto the inserts by cam-type operator means at another station of the assembly member. With such equipment, problems occasionally arise in connection with removal of the subassemblies from the assembly apparatus. In particular, the apparatus include means, typically in the form of radially disposed pistons carried by the assembly member for ejecting the inserts from the holding slots in a radial direction, i.e., substantially perpendicular to their direction of insertion into the holding slots. Additionally, the holding slots are fitted with means for laterally gripping opposite side edges of the inserts. So constructed, the gripping means tend to resist the radially directed expulsion forces exerted by the ejecting means. Such resistance is sometimes sufficient to prevent discharge of the subassemblies from their respective holding slots, thereby jamming the equipment and compressively damaging the inserts. In addition, the irregular shapes of such inserts many times causes the inserts to become misaligned with respect to the holding slots as the inserts are vertically fed into the slots. Mispositioning of the inserts, in turn, inhibits proper placement of the cutter bars onto the inserts. As a further drawback, the cam-type operator means presents the cutter bar at an angle with respect to the insert""s cutter cutter bar receiving structure whereby the cutter bar is rotated about the receiving structure as it is pressed thereon. If any of the cutter bar and insert spatial and positioning criteria are not completely satisfied, attachment of the cutter bar to the insert will likely fail and either or both of the insert and cutter bar may be damaged. Hence, the assembly process must be stopped and jammed or damaged parts must be removed, resulting once again in the production inefficiencies discussed above.
An advantage exists, therefore, for an apparatus and method for assembling the insert and cutter bar of a dental floss dispenser in a continuous, synchronous and reliable operation which minimizes manufacturing disruptions and the attendant downtime and costs associated therewith.
The present invention provides a system including an apparatus and method for assembling dental floss dispenser subassemblies which include an insert and a cutter bar. The insert typically comprises a body portion defining an arbor adapted to rotatably support a spool or bobbin wound with a length of dental floss and a superstructure contiguous with the body portion, the superstructure including cutter bar receiving structure onto which the cutter bar is adapted to be attached. The typical cutter bar is generally C-shaped in cross-section including an upper leg in which is formed the cutting blade portion, a lower leg, and a web connecting the upper and lower legs. The upper and lower legs are adapted to grip the insert""s cutter bar receiving structure when the cutter bar is installed thereon.
The instant apparatus includes a first conveyor for transporting inserts from a source of inserts to an assembly member. Likewise, the apparatus additionally comprises a second conveyor for transporting cutter bars from a source of cutter bars to the assembly member.
According to a presently preferred embodiment, the assembly member comprises a computer controlled, motor driven, rotatable wheel or disk having at least one or, more preferably, a plurality of holding slots or pockets adapted to securely yet gently receive inserts delivered from the first conveyor. During operation, the assembly member is indexed to a plurality of assembly stations. At a first assembly station the first conveyor delivers a leading insert into a holding pocket. From there, the motor indexes the rotatable wheel to a position where a first sensing device determines whether the insert has been properly inserted into the holding pocket. If an insert is properly inserted, the motor indexes the rotatable wheel to a second assembly station where a cutter bar may be placed onto the insert.
At the second assembly station the apparatus includes several strategically oriented components, namely, the discharge end of the second conveyor, stop means for aligning the leading cutter bar with the insert, and means for placing the cutter bar onto the insert. Upon the insert""s arrival at this station, the cutter bar placement means is activated push the cutter bar into press-fitting engagement with the cutter bar receiving structure to establish the cutter bar/insert subassembly. The placement means is then retracted to a xe2x80x9creadyxe2x80x9d position.
Following this, the wheel is rotated by the motor to a position where a second sensing device determines whether the cutter bar is absent or mispositioned with respect to the insert, i.e., whether the subassembly constitutes a xe2x80x9cgoodxe2x80x9d or a xe2x80x9cbadxe2x80x9d part. If it is determined that the subassembly is properly assembled, the computer commands the motor to index the wheel to a good part discharge site of a third assembly station. At this location means are provided to positively discharge the subassembly into a collecting bin for later placement along with a spool of dental floss into a dispenser case. If, however, the second sensing device determines that the subassembly is defective, the computer logic controls the motor to rotate the wheel to a bad or reject part discharge site of the third assembly station. At this location means are provided to positively discharge the defective subassembly into a reject part bin from which it may be further inspected and/or discarded.
The wheel is thereafter rotated to another position where there is located a third inspection device for determining if the subassembly, whether xe2x80x9cgoodxe2x80x9d or xe2x80x9cbad,xe2x80x9d has been properly discharged from the wheel. If no part is detected, the wheel is rotated to a xe2x80x9chomexe2x80x9d station where calibration of the assembly member may be effectuated (which typically occurs before an assembly production run is begun).
Lastly, the wheel is rotated to the first assembly station where it may receive another insert from the leading end of the first conveyor whereby the assembly process is repeated. As noted above, it is preferred that the wheel be constructed with a plurality of holding pockets such that several subassemblies may be simultaneously assembled.
The structural arrangement of the instant apparatus and its method of operation affords gentle and precise handling and assembly of the cutter bar and insert. It does so in a continuous, synchronous and reliable manner which reduces the likelihood of part jams, thereby enhancing assembly productivity while reducing manufacturing costs.
Other details, objects and advantages of the present invention will become apparent as the following description of the presently preferred embodiments and presently preferred methods of practicing the invention proceeds.